Saturday’s concert at the Pacific Amphitheatre will be his second such gig in a career spanning 50 years. The first was in Minnesota in the 1990s. The details escape him, he said — it's been so long.

Hardcore fans tend to flock to theaters and arenas, regardless of whether it’s a solo program or a tour by the Who. Fairs are a strange sort of fun because you can never be sure what you’re going to get, Daltrey admitted.

What about the OC Fair urged him to sign up, then?

“For a charity, I’ll play anywhere,” he responded.

The charity in question is Teen Cancer America, Daltrey’s pet project for the past two years. He spent a decade prior to that laying the groundwork in the United States.

“It’s just an anathema to me that, in this day and age, people in the medical community haven’t come to terms [with the fact] that teenagers are very different from children and adults,” he said, frustration rippling through his voice. “They get very different diseases, react very differently, need more psychological help and very little is done. It’s my aim to change that.”

The kids are all right

Daltrey is leading from the front, hoping that American bands will put their strength behind this initiative for adolescents ages 13 to 23. His goal is to highlight this demographic, which is otherwise erroneously swept into the categories of children or adults, he said.

What he calls the “cheaper end of care” is pegged to the construction of hospital units with professional services, specialized nursing and a teenage-friendly environment. Cautioning that he could discuss this topic for hours, Daltrey noted that one in every 360 boys and 420 girls is diagnosed with rare, aggressive strains of cancer. Late diagnoses and isolation make it worse.

In the past 25 years, the England-based Teen Cancer Trust has relied on the help of Daltrey and bandmate Pete Townshend, establishing more than two dozen wards — similar to dormitories — that create a venue for similarly stricken young patients to be in each other’s company.

Such facilities are met with enthusiasm by medical personnel and ailing adolescents, Teen Cancer America chair Rebecca Rothstein remarked. The teenage wings are a step up for many who have undergone treatment under the old system.

A believer that the best therapist for a teenager is another teenager, Daltrey, 69, recounted conversations with parents whose offspring struggled to express themselves. Add a cancer diagnosis to the mix and they go entirely inward, which he deemed “horrendous.”

“This isn’t a cupboard in a side hallway — there’s MTV,” he noted. “They can cook and be together. They can just be teenagers.”

Call it a bargain

In Costa Mesa, $1 from each ticket sold will be donated to the Who Cares Foundation, which funds Teen Cancer America’s efforts. Having forayed into the UCLA Medical Center, Daltrey is now looking to help other Southern California hospitals with oncology services for youths.

Originally, Doors keyboardist Ray Manzarek was scheduled to take the stage. When the 74-year-old passed away in May, OC Fair entertainment director Dan Gaines immediately honed in on his friend, Daltrey.